Computing Machinery I Assignment 05 Solution

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Description

Part A: Global Variables and Separate Compilation

A FIFO queue data structure can be implemented using an array, as shown in the following C program:

#include <stdio.h>

#include <stdlib.h>

#define QUEUESIZE

8

#define MODMASK

0x7

#define

FALSE

0

#define

TRUE

1

/* Function Prototypes */

void enqueue(int value);

int dequeue();

int queueFull();

int queueEmpty();

void display();

/* Global Variables */

int queue[QUEUESIZE];

int head = -1;

int tail = -1;

int main()

{

int operation, value;

do {

system(“clear”);

printf(“### Queue Operations ###\n\n”);

printf(“Press 1 – Enqueue, 2 – Dequeue, 3 – Display, 4 – Exit\n”);

printf(“Your option? “);

scanf(“%d”, &operation);

switch (operation) {

case 1:

printf(“\nEnter the positive integer value to be enqueued: “);

scanf(“%d”, &value);

enqueue(value);

break;

case 2:

value = dequeue();

if (value != -1)

printf(“\nDequeued value is %d\n”, value);

break;

case 3:

display();

break;

1

case 4:

printf(“\nTerminating program\n”);

exit(0);

default:

printf(“\nInvalid option! Try again.\n”);

break;

}

printf(“\nPress the return key to continue . . . “);

getchar();

getchar();

} while (operation != 4); return 0;

}

void enqueue(int value)

{

if (queueFull()) {

printf(“\nQueue overflow! Cannot enqueue into a full queue.\n”); return;

}

if (queueEmpty()) {

head = tail = 0;

} else {

tail = ++tail & MODMASK;

}

queue[tail] = value;

}

int dequeue()

{

register int value;

if (queueEmpty()) {

printf(“\nQueue underflow! Cannot dequeue from an empty queue.\n”); return (-1);

}

value = queue[head];

if (head == tail) {

head = tail = -1;

} else {

head = ++head & MODMASK;

}

return value;

}

int queueFull()

{

if (((tail + 1) & MODMASK) == head)

return TRUE;

else

return FALSE;

}

int queueEmpty()

{

if (head == -1)

return TRUE;

else

return FALSE;

}

2

void display()

{

register int i, j, count;

if (queueEmpty()) {

printf(“\nEmpty queue\n”);

return;

}

count = tail – head + 1;

if (count <= 0)

count += QUEUESIZE;

printf(“\nCurrent queue contents:\n”);

i = head;

for (j = 0; j < count; j++) {

printf(“ %d”, queue[i]);

if (i == head) {

printf(” <– head of queue”);

}

if (i == tail) {

printf(” <– tail of queue”);

}

printf(“\n”);

i = ++i & MODMASK;

}

}

Translate all functions except main() into ARMv8 assembly language and put them into a separate assembly source code file called a5a.asm. These functions will be called from the main() function given above, which will be in its own C source code file called a5aMain.c. Also move the global variables into a5a.asm. Your assembly functions will call the printf() library routine. Be sure to handle the global variables and format strings in the appropriate way. Input will come from standard input. Run the program to show that it is working as expected, capturing its output using the script UNIX command, and name the output file script1.txt.

Part B: External Pointer Arrays and Command-Line Arguments

Given the following declarations in C:

char *month[] = {“January”, “February”, “March”, “April”, “May”, “June”, “July”, “August”, “September”, “October”, “November”, “December”};

char *season[] = {“Winter”, “Spring”, “Summer”, “Fall”};

Create an ARMv8 assembly language program to accept as command line arguments two strings representing a date in the format mm dd. Your program will print the name of month, the day (with the appropriate suffix), and the season for this date. For example:

./a5b 12 25

December 25th is Winter

3

Be sure to use the proper suffix for the day of the month. For example, one should distinguish the 11th from the 1st, 21st, and 31st. Your program should exit, printing this error message, if the user does not supply two command-line arguments:

usage: a5b mm dd

You will need to call atoi() to convert strings to numbers, and printf() to produce the output. Be sure to do range checking for the day and month. Assume that Winter ranges from December 21 to March 20, Spring from March 21 to June 20, Summer from June 21 to September 20, and Fall from September 21 to December 20. Name your source code file a5b.asm. Run your program three times with different input to illustrate that it works; capture the output using the script UNIX command. Name the output file script2.txt.

New Skills Needed for this Assignment:

  • Understanding and use of external variables in assembly.

  • Separate compilation.

  • Calling assembly functions from main().

  • Calling library functions from assembly routines.

  • External arrays of pointers.

  • Command line arguments.

Submit the following:

Your source code and 2 scripts via electronic submission. Use the Assignment 5 Dropbox Folder in D2L to submit electronically. Your TA will assemble and run your programs to test them. Name your files a5aMain.c and a5a.asm for Part A, and a5b.asm for Part B, and the scripts as script1.txt and script2.txt.

4

Marking Criteria

Part A:

Correct use of external variable(s)

4

______

enqueue() function in assembly

4

______

dequeue() function in assembly

4

______

queueFull() function in assembly

4

______

queueEmpty() function in assembly

4

______

display() function in assembly

8

______

Linking of separate source code modules

2

______

Correct manipulation of queue

4

______

Part B:

Command line arguments

4

______

Correct use of external pointer arrays

4

______

Calls to library functions

2

______

Range checking

3

______

Correct output

4

______

2 Scripts showing I/O

4

______

Complete documentation and commenting

4

______

Design quality

4

______

Total

63

______

5